LHC Startup at 10 TeV

Robert Aymar, the Director General of CERN, has announced that the LHC will operate when it starts up this year at an energy of 5 TeV per beam (10 TeV total center of mass energy), rather than the design energy of 7 TeV per beam. To operate the LHC magnets at the highest current and get to 7 TeV requires a time-consuming sequence of powering tests and quenches, so the decision was made to put this off until the winter shutdown. With this decision, the process of beam commissioning can start soon after all sectors have been cooled down, and this is now scheduled for mid-June. Beam commissioning should take two months, with first physics collisions thus scheduled for late summer.

It remains possible that problems will be found during or after cooldown that will require warming back up one or more sectors, and this would lead to a delay of a couple months or so. The last sector scheduled to be cooled down is 4-5, which is now warm to allow repair of the defective triplet magnets. Whenever a sector is warmed up, a major problem is damage to defective PIMs which then need to be replaced. If there are too many of these, a delay in the cooldown is possible. The search for damaged PIMs relies on a “sputnik” tennis-ball-like sensor sent through the beam-pipe. Latest news is that 4 damaged PIMS have been found so far.

Update: I’d been wondering how much extra work this change in energy would cause for the experimentalists, just saw a posting about this by Gordon Watts, entitled Start Your Monte-Carlo Engines!

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17 Responses to LHC Startup at 10 TeV

  1. D R Lunsford says:

    Whoa there. This is a matter for the courts, Peter.


    The laws of physics. PN injunction!


  2. Peter Woit says:

    I did see the NYT story about the lawsuit this morning, and half a dozen blogs already have postings about it. As far as I can tell, no court is going to take this seriously, so it’s unclear why this story deserves any attention, much less ending up on the front page of the Times.

  3. Domenic says:

    Hey Peter,

    As an undergrad, this is the first time in my life I’ve watched a new particle accelerator go through the birthing process. My impression is that the LHC is kinda sucking at it—lots of delays, problems, subpar results, etc. But, I have no basis for comparison, so I thought I’d ask someone who’s been around long enough to know: is this typical?

    Thanks :).

  4. Peter Woit says:


    I don’t think the LHC problems and delays have been at all unusual for a project of this magnitude. For a comparison you’d have to go back to the early 80s (Tevatron) or late 80s (LEP), to see how those projects went as they approached beam commissioning. But the LHC is a more ambitious endeavor than either of those, and it is receiving a lot more attention.

    The crucial period will probably be this summer and fall when they start trying to store a beam in the machine and get a useful luminosity. If this goes smoothly, the thing will be quite a big technical success, even though it would end up being a couple years behind early optimistic schedules.

  5. Domenic says:

    Thanks Peter, I thought that might be the case. Well then, here’s hoping! It’d be pretty amazing to go into grad school (2.5 years from now) with some LHC data to guide me.

  6. milkshake says:

    About that lawsuit: Here is a photo of a black drainhole at Monticello. (Coming soon to Lake Geneva):


  7. wb says:


    Not to find fault with the LHC progress but rather to give some additional perspective, I would point out that the PEP-II and KEK-B B-factories were commissioned extremely rapidly. Rapid commissioning is also commonplace these days with synchrotron light sources. RHIC also went fairly smoothly. Regarding LHC one must keep in mind that this is by far the most difficult and largest collider ever built. Moreover it has a enormous stored energy in the beam, the magnets and the fluid systems.

    While we all would have liked to see collisions earlier, the LHC team must be applauded for their steady and systematic progress. Likewise the decision to begin collisions at 10 TeV is a prudent one. There is great physics awaiting us.

    As for the law suit… the less said the better.

  8. YBM says:

    Dear Peter,

    this is related only by Motl adding this postscript to a post of him on the LHC :

    P.S.: Let me say something about the titles. Of course, I do know that the title is routinely chosen by the editor or the publisher. That was the case of “The Bogdanov Equation”, too. On the other hand, I am convinced that the author always has to approve it. Although it was a bit of a shock to see the cover of the book for the first time, I of course fully confess that I approved it after a little thought accompanied by mixed feelings even though this title is arguably not the most accurate description of the content of the book. Whether someone including myself likes it or not, I am responsible for the title. In the very same way, I am convinced that the titles such as “The Trouble With Physics” and “String Theory’s Latest Folly” were approved by the authors, too. Trying to get rid of the responsibility – whenever the title becomes inconvenient – is an unfair game.

    Do you know of any reason or event making Lubos to regret his french book ? Apart of him getting miracously some kind of intellectual honesty (which I doubt)…

  9. Peter Woit says:


    That comment of Lubos’s was in response to Krauss writing in to say that he was not responsible for the headline put on his article in New Scientist. Lubos seems not to understand the difference between a book (where the author definitely has a say about the title) and a magazine article (where the author doesn’t). The way he writes about this, one gets the impression that the title was chosen by someone else. It’s definitely a curious book, quite possibly there were other hands at work creating the thing than just its official author….

  10. Harry says:

    Anyway (and off-topic, sorry),

    “the Bogdanov Equation” is a phenomenal success in France : it just took the record of the best-selling book for its first month (this record was previously hold by “Harry Potter and the Deathly Hallows”)

    Unbelievable !

  11. Hans says:

    @ Harry

    according to which source?
    The book doesent even figure in the FNAC top 100 and holds place 19 on the FNAC science and culture list. On amazon.fr it has the rank 2,059 (thought #1 in Physics). Sure, this is not bad, but not exactly Harry Potter. ..

  12. Peter Woit says:


    I had assumed that Harry’s comment was an attempt at April 1 humor.

    Actually, if I had first heard of the Lubos-Bogdanov book on April 1, I would have been 100% convinced the whole idea was an April Fool’s joke.

  13. Harry says:

    Yes, it was indeed an attempt of April Fool’s joke 🙂
    (Sorry, I could not resist.)

  14. Hans says:

    Ok, I got fooled!
    And i actually spent 10 minutes checking the sources!

  15. piscator says:

    hey peter,

    back to the topic of the post: any idea what is happening with the LHC? In the last day and a half or so all the sectors that were previously being cooled down now all seem to be being warmed up…..


  16. Peter Woit says:


    Maybe this has something to do with “Open Days”. On the 5th and 6th they’ll be opening the lab up for visitors, may be that the cooldown is being stopped during that period.

    I haven’t heard of any problems, and don’t see anything unusual at their web-site. They finished warming back up one of the sectors (4-5) a while ago, now are looking there for defective PIMS, have found 9. Supposedly more than 24 will be a problem. They just started cooling down 6-7, three other sectors are being cooled down now. Maybe they’re stopping this for a few days…

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